Understanding the coupling between structural phase transitions and thermal transport is essential for designing functional materials with tunable properties. Here, we investigate this interplay in ${\mathrm{CaSnF}}_6$ by combining first-principles calculations with a machine-learned neuroevolution potential that enables large-scale molecular dynamics simulations across a wide temperature range. The simulations accurately capture the first-order structural phase transition and associated lattice dynamics. We show that the negative thermal expansion originates from low-energy rigid unit modes involving cooperative rotations of corner-sharing ${[\mathrm{CaF}}_6{]}^{4-}$ and ${[\mathrm{SnF}}_6{]}^{2-}$ octahedras, which induce bond-angle bending and volume contraction. At the same time, strong anharmonicity, dominated by four-phonon scattering, plays a central role in suppressing lattice thermal conductivity $\left({\kappa }_L\right)$. Crucially, nonequilibrium simulations reveal a pronounced nonmonotonic anomaly in ${\kappa }_L$ near the phase transition, deviating from the conventional $\sim 1/T^{\alpha }$ behavior and providing direct transport evidence of lattice reconstruction. These results establish a unified mechanism linking lattice geometry, anharmonic vibrational dynamics, and thermal transport, and highlight the potential of machine-learned potentials for bridging atomic-scale phase transitions with macroscopic transport properties.

Strain engineering is an effective route to tune electron mobilities in two-dimensional transition metal dichalcogenides, but the underlying physical mechanisms are not yet fully uncovered. In this work, we employ ab initio Boltzmann transport calculations to investigate the evolution of electron mobility in transition metal dichalcogenides $M{X}_2$ $(M=\mathrm{Mo}, \mathrm{W}, \mathrm{Zr}, \mathrm{Hf}; X=\mathrm{S}, \mathrm{Se})$ under biaxial tensile strain. The electron mobilities of hexagonal monolayer $M{X}_2$ $(M=\mathrm{Mo}, \mathrm{W})$ increase under tensile strain. We trace this enhancement to a strain-induced downward shift of the K valley in the conduction band, which enlarges the energy separation between the K and Q valleys. This shift is driven by weakened $d_{z^2}$-orbital coupling, which in turn suppresses electron-phonon scattering. This work uncovers the microscopic mechanism underlying strain-induced enhancement of electron mobility and identifies orbital coupling as a practical design route for optimizing transport properties in two-dimensional semiconductors.

We find an exact nonequilibrium steady state of an open dissipatively driven XXZ spin-$\frac{1}{2}$ chain with source or sink spin bath at one end and an arbitrarily oriented boundary field at the other end.

Lateral heterostructures of transition-metal dichalcogenides (TMDs) host spatially separated charge-transfer (CT) excitons. While analogous to interlayer excitons in vertical TMD heterostructures, these interfacial excitons possess much larger in-plane dipoles of several nanometers and an additional center-of-mass quantization. Here, we investigate mutual interactions between these highly dipolar CT excitons using a quantum mechanical approach. Accounting for the dipolar and quantum exchange interactions, we evaluate the experimentally accessible density-dependent energy renormalization and predict a net energy blueshift of a few meV for bound CT excitons. Interestingly, for small dipole moments, the energy renormalization displays a quadratic dependence with respect to the dipole moment, in contrast to the linear dependence found in vertical TMD heterostructures. We show that spatial energy offset and temperature are the key tuning knobs for controlling the density-dependent excitonic response. Overall, our results contribute to a better microscopic understanding of CT excitons and their interactions in lateral TMD heterostructures.

Weak topological insulators are conventionally characterized by weak $\left(Z_2\right)$ indices and are usually distinguished from strong topological insulators by the appearance of an even number of surface Dirac cones. We show that this description misses an essential signed structure: weak topological surfaces with the same number of Dirac cones can either carry a nonzero net chirality or be chirality compensated. This distinction is invisible to the weak indices. We derive a bulk-to-surface projection theory in which the chirality of each surface Dirac cone is determined by the surface-projected orientation of the corresponding bulk band-inversion Dirac sector. As a minimal demonstration, we construct two time-reversal-invariant lattice models with the same weak indices and the same surface Dirac-cone locations, but with opposite and identical cone chiralities, respectively. The resulting net surface chirality directly controls whether magnetic surface responses add or cancel. Our results provide a chirality-resolved refinement of weak topological surfaces beyond the conventional weak-index classification.

Jahn-Teller (JT) distortions are a key driver of physical properties in many correlated oxide materials. Cooperative JT distortions, in which long-range orbital order reduces the symmetry of the average structure, are common in JT-distorted materials at low temperatures. This long-range order will often melt on heating via a transition to a high-temperature state without long-range orbital order. The nature of this transition has been observed to vary with different materials depending on crystal structure; in ${\mathrm{LaMnO}}_3$, the transition has generally been interpreted as order-disorder, whereas in layered nickelates $A{\mathrm{NiO}}_2$ $(A=\mathrm{Li},\mathrm{Na})$, there is a displacive transition. However, authors of recent theoretical work have suggested that previous evidence for order-disorder may in fact be a consequence of phonon anharmonicity rather than persistence of JT distortions. In this work, we run Monte Carlo simulations with a simple Hamiltonian that is modified to include terms dependent on the JT amplitude $\rho$, which is allowed to vary within the simulation. Our simulations yield distributions of JT amplitudes consistent with displacive rather than order-disorder behavior for both perovskites and layered nickelates. We also find significant differences between the transition observed for perovskites compared with layered nickelates, which we attribute to differing extensivity of configurational entropy on the two lattices, suggesting a crucial role for lattice geometry in determining behavior.

We theoretically study spin pumping into a spin-nematic state in a junction system composed of a ferromagnetic insulator and a spin-nematic insulator, described by using the spin-1 bilinear-biquadratic model. We analyze the increase of the Gilbert damping in ferromagnetic resonance due to an interfacial exchange coupling within a mean-field theory based on the Schwinger boson method. We find that the two Schwinger bosons contribute in distinct ways to spin pumping. We report a detailed dependence of the spin pumping on a resonant frequency and a magnetic field, along with a comparison to the case of the canted antiferromagnetic insulator. Our findings establish spin pumping as a relevant technique to verify and characterize spin-nematic phases.

We examine plasma excitations with linear dispersion in a system of superconducting electrons in thin NbN disks. Using frequency-domain terahertz spectroscopy, we study the evolution of plasmons up to critical temperature $T_c$. The observed excitations tend to shift to the lower frequencies while temperature is increasing and the spectral features vanish at $T>T_c$. We study the dependence of the plasma velocity on superconducting electron density $n_s$, a NbN layer thickness $t$, and disk diameter $d$. The velocity appears to be independent from the disk diameter and period while having a square-root dependency on the parameter $n_{s}t$.

The study of plastic deformation of magnesium oxide (MgO) is of great significance for both materials science and geoscience. In this work, we systematically investigate the plastic deformation of two grain sizes of MgO under cyclic compression using diamond anvil cell (DAC). The morphology, grain size, and aspect ratio of grain axis contrast of the postdeformed samples indicate that plasticity is accommodated primarily by grain fracture in coarse-grained MgO, whereas grain coalescence and grain growth resulting from grain rotation and realignment are observed in fine-grained MgO. Furthermore, an unexpected {111}〈11–2〉 slip, attributed to the dissociation of full 〈110〉 dislocations driven by high cyclic stress, is identified in MgO. These findings highlight the significance of high-pressure cyclic loading in activating unusual plastic deformation mechanisms of MgO, with implications for material design and understanding of seismic anisotropy in Earth's lower mantle.

Using the quantum effective action in the Schwinger-Keldysh formalism, we derive quantum-thermal corrections to the semiclassical dynamics of a dissipative system described by a macroscopic degree of freedom. We discuss the connection with the Ehrenfest theorem and, within the local potential approximation, obtain the corrections in closed form for arbitrary temperature and damping, showing that as the temperature increases, they cross over from purely quantum to purely thermal. In the low-temperature and weak-damping regime, corrections are set by the zero-point energy of fluctuations evaluated at the classical underdamped frequency, closely paralleling the conservative case, which allows us to go to higher order in the derivative expansion. We apply these general results to the resistively and capacitively shunted superconducting Josephson junction and to an elongated bosonic junction, where corrections can reach the percent level under realistic conditions.

We explore the spectral properties of the four-fermion Sachdev-Ye-Kitaev model with interaction sourced from a Lévy stable (fat-tailed) distribution. We study the eigenvalue distribution, focusing on long- and short-range correlations and extreme statistics. Our analysis uncovers a crossover from chaotic to integrable behavior (in the spectral correlations) as the distribution becomes increasingly fat-tailed. We investigate this crossover through a hierarchical analysis of the eigenvalue spectrum, based on the multifractal hierarchy of the Lévy stable distribution. The crossover is explained in terms of a genuine many-body effect, which is distinct from the single-particle transition (controlled by a mobility edge) of the underlying Lévy random matrices. We conclude with comments on the model's solvability and discussion of possible models with exact transitions.

The nonlinear effects in strongly driven magnetic and spintronic devices are gradually becoming key challenges in their practical applications and physical understanding. Here, an analytical theory of nonlinear ferromagnetic resonance is developed by solving the Landau-Lifshitz-Gilbert equation in the presence of a uniaxial anisotropy field under arbitrary microwave excitation. The solution shows that the magnetization undergoes stable conical precession, allowing the nonlinear resonance condition, resonance field, linewidth, and switching boundaries to be obtained analytically. The analysis reveals that the anisotropic-induced nonlinear restoring force is responsible for the asymmetric foldover resonance and the power-dependent resonance shift, in excellent agreement with spin-pumping measurements on ${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}/\mathrm{Pt}$ bilayers. By incorporating the microwave current-induced spin-transfer torque, we further show that the ac spin-transfer torque acts as a phase-sensitive perturbation that modifies the stability of nonlinear precession without changing the nonlinear resonance condition, thereby modulating the up-jump field. This work provides a unified analytical framework for understanding nonlinear foldover resonance and spin-transfer torque modulated magnetization dynamics.

Electron-phonon coupling is at the origin of conventional superconductivity, enabling the pairing of electrons into Cooper pairs. The electron-phonon matrix elements depend on the electronic eigenstates and, in the standard linear approximation, on the first derivative of the potential felt by the electrons with respect to ionic perturbations. Here, we focus on the derivatives of the potential with a twofold aim: to assess their contribution to the overall coupling and to analyze the limitations of neglecting higher-order derivatives. Several real-space functions are proposed to do the analysis, and are computed for some well-known superconductors. Our results show that, in hydrides, the derivatives of the potential tend to be larger in regions of high electron localization, explaining the success of electronic descriptors previously observed to correlate with the critical temperature. The new functions introduced here are able to tell apart structures with similar types of bonding but very different critical temperatures, such as ${\mathrm{H}}_3\mathrm{S}$ and ${\mathrm{H}}_3\mathrm{Se} Im\overline{3}m$ phases, where electronic descriptors alone fail. Moreover, they provide a method to discriminate promising superconductors from conventional low-$T_c$ materials. Interestingly, our descriptors are capable of easily estimating the impact of higher-order terms in the electron-phonon coupling. In fact, we capture the limitations of the linear approximation expected for PdH, and we predict an even more important nonlinear behavior in other hydrides.

Two-dimensional Rokhsar-Kivelson (RK) dimer models on bipartite lattices are generally limited to translation-symmetry-broken dimer crystals. We introduce a tensor-product regularization of the dimer Hilbert space that yields a qubit Hamiltonian interpolating from the RK model to the $\pi$-flux toric code, thereby accessing a deconfined ${\mathbb{Z}}_2$ topological liquid. In this framework, the ${\mathbb{Z}}_2$ liquid descends from a multicritical $U\left(1\right)$ spin liquid through condensation of a charge-2 Higgs field, thus avoiding confinement. Using iDMRG together with low-energy field theory, we determine a phase diagram containing two continuous quantum phase transitions—a $3\mathrm{D} {\mathrm{XY}}^{*}$ transition between the ${\mathbb{Z}}_2$ liquid and the columnar/plaquette-VBS, and a quantum Lifshitz transition between two dimer crystals—alongside a first-order transition between the staggered crystal and the ${\mathbb{Z}}_2$ liquid. Our field theory suggests a deconfined multicritical point described by an Abelian Higgs model with dynamical critical exponent, $z=2$, where the three transitions meet, highlighting the interplay of fractionalization and emergent gauge fluctuations.

Quantum-dot-based platforms offer a promising route towards realizing the Kitaev chain Hamiltonian hosting Majorana bound states (MBSs). Poor man's MBSs arise in a two-site Kitaev chain when the parameters of the system are fine tuned to the sweet spot. Based on our previous work [A. Gómez-León et al., Phys. Rev. B 111, 155410 (2025)], we consider a microscopic model for the Kitaev chain based on quantum dots with proximity effect embedded in a photonic cavity. We find that the photon coupling in the microscopic model yields an effective Hamiltonian where the cavity affects the pairing term. However, we demonstrate that even in this case, it is possible to screen particle interactions and reach the sweet-spot condition for the emergence of the poor man's MBSs. In particular, we find that attractive particle interactions can be canceled for the cavity prepared in the zero-photon state, while repulsive ones can be screened with a cavity prepared in the one-photon state. Furthermore, in the case of a large number of photons in the cavity, we find that the hopping amplitudes are suppressed, resulting in a degenerate spectrum. This motivates the use of quantum light for engineering poor man's MBSs with cavity embedding.

Intrinsic defects govern carrier trapping and recombination in two-dimensional semiconductors, yet the microscopic origin of defect-dependent capture dynamics remains unclear. Here, we compute carrier capture coefficients of vacancy defects, treating monolayer ${\mathrm{MoS}}_2$ as a prototype, from first principles. We find that the sulfur monovacancy is present 0.25 eV below the conduction band and has a capture coefficient of $\sim {10}^{-15}{\mathrm{cm}}^3/\mathrm{s}$. In contrast, the sulfur divacancy exhibits a seven-orders-of-magnitude higher capture coefficient ($\sim {10}^{-8}{\mathrm{cm}}^3/\mathrm{s}$), despite being only moderately deeper in energy. This enhancement originates from strong lattice relaxation enabling efficient multiphonon capture. Consequently, monovacancies contribute weakly to trapping, while sulfur divacancies dominate nonradiative recombination and reduce quantum yield. In contrast, molybdenum vacancies and sulfur antisites contribute to deep level states with smaller capture coefficients, indicating a limited role in carrier trapping in $n$-type devices.

Nonequilibrium control of electronic properties in condensed matter systems can result in novel phenomena. In this work, we provide a nonequilibrium route to realize half-metallic phases. We explore the periodically driven Hubbard model on a bipartite lattice and demonstrate that a specially designed sublattice-dependent drive can transform a weakly interacting metal or insulator into a ferrimagnetic half-metal (HM). We consider a Fermi-Hubbard model with only nearest-neighbor hopping and Floquet engineer the elusive half-metal phase by driving the site potentials periodically. The drive induces staggered higher-range hoppings and a staggered potential between two sublattices in the Floquet Hamiltonian. Close to the dynamical localization point, due to the suppression of nearest neighbor hopping in the driven system, an effective enhancement of various terms in the Floquet Hamiltonian, including the e-e interactions, occurs. This helps in stabilizing a broad ferrimagnetic HM phase for a wide range of drive parameters. This dynamically stabilized HM phase is a pristine platform for next-generation spintronics, topological quantum computing (specifically for engineering Majorana zero modes in hybrid nanowires) and ultrafast magnetic memory architectures.

Achieving the decoupling of lattice thermal conductivity and electrical transport remains a central challenge in thermoelectric materials. Here, based on first-principles calculations and anharmonic lattice dynamics, we show that lone-pair-driven orbit-lattice coupling in quasi-one-dimensional halides $\mathrm{Tl}{X}_3$ ($X=\mathrm{Br},\mathrm{I}$) simultaneously enables ultralow lattice thermal conductivity and high thermoelectric performance. We reveal that the stereochemically active Tl-$6s^2$ lone-pair electrons, through $s\text{−}p$ hybridization and antibonding interactions, induce off-center distortions via a pseudo-Jahn-Teller mechanism, leading to highly polarizable bonding, softened interatomic force constants, and pronounced lattice anharmonicity. This electronically driven lattice instability strongly suppresses phonon group velocities and lifetimes, resulting in ultralow lattice thermal conductivities of 0.13 and 0.16 ${\mathrm{Wm}}^{-1}{\mathrm{K}}^{-1}$ along the $b$ axis for ${\mathrm{TlI}}_3$ and ${\mathrm{TlBr}}_3$ at 300 K, respectively. Concurrently, spin-orbit coupling induces band convergence near the valence band maximum, enhancing valley degeneracy and improving the $p$-type Seebeck coefficient without completely suppressing carrier transport, thereby leading to moderate but beneficial power factors. As a result, peak $ZT$ values of 2.22 (700 K) for $p$-type ${\mathrm{TlBr}}_3$ and 1.91 (800 K) for $p$-type ${\mathrm{TlI}}_3$ are achieved, while $n$-type ${\mathrm{TlI}}_3$ exhibits a competitive $ZT$ of 0.85 at 800 K. Our results establish orbit-lattice coupling as a unifying mechanism for achieving phonon-glass-like thermal transport and high thermoelectric performance, providing useful design insights for the development of next-generation thermoelectric materials.